1. Field of the invention
The invention relates to an optical system of variable magnification having multilens-array units and a method for varying magnification of the same.
2. Description of the prior art
In order to make compact photocopy machines, it has been proposed to apply multilens-arrays as an optical system to photocopy machines, instead of conventional spherical lenses having large apertures. Examples of these arrays are a convergent light-transmitter such as a Selfoc lens (trade name, Nippon Ita Glass Co., Japan), a microlens and a DAHA prism lens, all of which are composed of superposed lenses. Such optical systems do not provide a function of variable magnification, forming only an image in the same size as an object. Although such optical systems will be theoretically capable of enlarging or reducing an original with the desired overall magnification by two scanning processes, one of which allows an enlargement or reduction of the original in the main scanning direction and the other of which allows an enlargement or reduction thereof in the remaining sub-scanning direction, they require the two copying processes, which result in a complex copying system.
An alternative lens system is a zoom-type lens which, while providing variable magnification, is necessarily long, requiring a large housing and an increased size of the copy machine as a whole.